The subject matter disclosed herein relates to a locking device arrangement for a rotating bladed stage.
Rotating bladed stages (i.e., wheels) in gas turbine engines with circumferential dovetail attachments require a radial load slot for blade installation and typically two adjacent radial lock slots for blade locks, one on each side of the load slot. The blade locks prevent blades from working their way back out of the radial load slot.
The radial load slot and the adjacent radial lock slots, however, form a set of three slots that tend to create an inherent unbalance of the rotating mass in the wheel relative to the axis of rotation and a potentially high accumulation of flow path gaps. Indeed, material removed to create the three slots represents a loss of material on one side of the wheel. Since balance correction operations for wheels are usually done with the locking devices installed, the material lost for the lock slots is more than offset by the weight of the adjacent locking devices. The residual unbalance of the slot set with the blade locks installed can still be fairly significant requiring the addition of multiple balance weights for correction.
Furthermore, a significant gap can be produced between blade platforms that cause air leakage (thus reducing the engine performance and efficiency) and aerodynamic disturbances in the flow path. The maximum circumferential gap between blade platforms that can be accumulated is a result of the inherent manufacturing tolerances in the platform widths, the thermal and mechanical radial growth of the wheel and blades, and the number of blades between locker devices.